Tfl 435 
.W75 
Copy 1 



VOL. IV BULLETIN NO. I 



Iowa State College 
Engineering Experiment Station 



hi] 



Tests of Iowa Limes 

BY IRA A. WILLIAMS 



JULY, 1907 
AMES, IOWA 



Published by the Iowa State College Engineering Experiment Station, 
Ames, Iowa, Bi-Monthly, in February, April, June, August, October and 
December, each year. 

Application filed for admission at Postoffice at Ames, Iowa, as second 
class matter. 

Mr ' 



Engineering Experiment Station 
IOWA STATE COLLEGE 

Ames, Iowa 



STATION STAFF 

President A. B. Storms Ex-Officio 

Director A. Marston Civil Engineering 

Professor W. H. Meeker Mechanical Engineering 

Professor L. B. Spinney Electrical Engineering 

Professor S. W. Beyer .Mining Engineering 



BULLETIN 

Vol. IV No. 1 



Mining Engineering Section 

Tests of Iowa Limes 



JULY 1907 



<o 

*° L 1 



^ ^ 



<v 



CONTENTS 

General Considerations 3 

White versus Brown Limes 4 

White versus Argillaceous and Siliceous Limes 4 

Slaking 8 

Setting and Hardening 11 

Lime Mortar . 13 

Tests of Lime Mortars '. 14 

High Calcium White Limes 

Mason City, Iowa _ 16 

Spriugfield, Mo;. 24 

Magnesian and Dolomitic Limes 

Eagle Point, Iowa, Brown Lime 30 

Mason City, Iowa, Brown Lime 36 

Maquoketa White Lime and Excelsior White Lime 41 

"New Process Lime", Voila, Iowa 51 

General Conclusions 56 

TABLES AND FIGURES 

Analysis of Natural Cements '... 7 

Physical Tests of Ohio Limes. 18 

Breaking Strength of Briquettes made with Mason City White Lime. ...20-22 

Springfield, Mo., White Lime... 26-27 

Eagle Point orown Lime 32-33 

Mason City Brown Lime 37-38 

Excelsior White Lime , 42-44 

Maquoketa White Lime 43-47 

Viola "New Process Lime" .-. 52-53 



n. OF D. 
'.' 6 i9!3 



TESTS OF IOWA LIMES. 

BY IRA A. WILLIAMS 
GENERAL CONSIDERATIONS 

The lime of commerce is produced by the calcination of 
limestone and varies in composition and purity therefore 
as do the limestones themselves. The latter range from 
practically pure calcium carbonate (CaC0 3 ) to the sandy 
and clayey limestones in which the impurities compose a 
large percentage of the rock. Again, the calcium may be 
in part replaced by magnesium which gives the magnesian 
limestones, and if this replacement has taken place to 
the extent that magnesia (MgO) comprises eighteen to 
twenty per cent of the stone, the term dolomitic lime- 
stone is more commonly applied. 

A limestone composed essentially of CaC0 3 will furnish 
a high grade of quicklime, one containing little else than 
CaO; one composed of CaCO B with a greater or less per- 
centage of MgC0 3 will afford a magnesian or dolomitic 
lime; while the argillaceous limestones will give a product 
of a degree of purity depending on the amount of clay. 
in the original stone.' The properties of the resulting 
limes will vary according to their composition. 

Limestones are widely distributed in nature, both geo- 
graphically and geologically. They are found inter- 
bedded with and overlapping other common sedimentary 
strata, and they have been produced in much the same 
way as other sedimentary rocks. Good reasons are readi- 
ly conceived why they should be apt to partake of the 
nature of, and to grade into or be, contaminated with 
other sedimentary materials. It is, nevertheless, not at 
all uncommon to find limestones that run over ninety per 
cent lime carbonate, and occasionally as high as ninety- 
eight or ninety-nine per cent. The analysis of nine sam- 
ples of non-dolomitic Iowa limestones show a range of 
from 82.5 to 97.02 per cent carbonate of lime, three of the 
nine samples showing over ninety per cent. 

As indicated, limestones depart in composition most 
commonly in the content of magnesia and in the clay 
and sand impurities. The effect of these substances on 
the resulting lime is of so much importance that they 
may be given separate consideration. 



3. Hydraulic or Roman cements 

4. Portland cement. 

The points of , distinction between . 1 and 2 have been 
noted. In composition, 2 and 3 are not separable; By 
an increased temperature in burning some hydraulic 
limes will become hydraulic cements. Twenty-four per 
cent of clay is- about the permissible upper ,: mit tor the 
hydraulic limes, while Roman cements are in use which 
contain but little over twenty per. cent ol clayey impurities, 
contain but little over twenty per cent of clayey im- 
purities. The chief distinguishing feature of these two 
groups lies in the ability of the limes to slake to a paste 
with water without previous pulverization. Fine grind- 
ing is necessary before water will affect appreciably Ro- 
man cements and before they will harden as a mortar. 

The feeble hydraulicity of the limes and the relatively 
strong of the cements would appear to be due to the vary- 
ing degree to which chemical combination has been 
brought about in burning. In lime burning, little if any 
chemical action occurs between the lime and the clay. 
What does take place tends to produce an unstable or 
1 unlocked' condition of the clay and other siliceous ma- 
terials such, that in the presence of water, the lime hy- 
drate slowly attacks these and combines with them to 
form silicates that are harder and more durable than 
lime mortar. Clinkering in burning, is an indication of 
chemical action, further progress in rendering available 
and susceptible to the attack of the lime and water the 
clay and other siliceous substances in the stone. Burn?"! 
to this condition, the product is properly termed a cement 
and in use attains a stony hardness and relatively great 
permanency. 

Hydraulic or Roman cements are spoken of also as nat- 
ural or rock cements, since they are made from lime- 
stones in which the ingredients occur naturally in the 
proper proportions. Such limestones are found in dif- 
ferent parts of the United States, but have been utilized 
principally in the Appalachian states of the East and 
along the Ohio river. The actual composition ranges be- 
tween wide limits as shown in the table below in which 
are compiled the analyses of five reputable brands of 
natural cements. ■ < ■ 



ANALYSIS OF NATURAL CFMFNTS. 



NAME 







<L> 








































X 




X 




















Hi 


-» 


E 




z> 


c 




£ 




it 










c/5 


< 


fc 


_: 


^ 



c o 



"Fern Leaf" brand 

Louisville, Fy. 

N. L. & C. Co. 

Rosendale, N. Y. 

•■ I F't'fnian" 

Rosendale, X. Y. 

"Utica" Brand 

Utica, 111. 



Mankato, Minn. 



26.40 


6 . 28 


1.00 


45 . 22 


9.00 


30.50 


6.84 


2 . 42 


34 38 


18.00 


27.30 


7.14 


1.S0 


35 . 98 


18.00 


27 . '30 


10 60 


0.80 


33.04 


7 . 26 


28.43 


6.71 


1.94 


36.31 


23 ! 89 



4.24 



7.86 



3.98 3.78 



6.80 
7.42 
1.80 



2.98 
2.00 
0.92 



Numbers 3 and 4 in the outline on page 6 bear to 
some extent a similar relation to that briefly given for 2 
and 3. A more complete vitrification of the ingredients 
in the cement mixture until they issue from the kiln as 
thoroughly vitrified clinker produces the maximum 
amount of hydraulic silicate. The chemical changes 
which occur in burning are complicated and become more 
so the higher the temperature over that employed in the 
manufacture of natural cement. Just what these changes 
are is not accurately known, but experimentation has 
determined within fairly narrow limits what proportions 
of the various constituents entering into a mixture of 
clay, silica and limestone will produce the greatest 
amount of unstable, hydraulic silicate, and what temper- 
atures are required to accomplish this result. These pro- 
portions and temperatures are employed in the manufac- 
ture of Portland cement. 

The foregoing remarks will serve to show the relation 
of limes as a mortar material to other substances used 
for a similar purpose. This paper has to do with limes 
nlone and the several physical properties of the latter 
that are of chief importance will be briefly discussed. 

SLAKING. 

The property belonging to limes which makes them of 



industrial value is their ability to slake or crumble to a 
powder on the addition of water, and to harden when 
allowed to stand in contact with the atmosphere. The 
reaction which occurs in slaking has already been given. 
If a lime is properly burned, all lime carbonate in the 
original stone has lost its carbon dioxide, and become 
quicklime (CaO). It is the rapid change accompanied by 
the evolution of heat when water is added that causes 
lime to slake. 

Slaking is a physical evidence of the hydration of lime, 
but it is not to be understood that slaking is a necessary 
result of such chemical action. The two processes are 
really distinct. The exposure of caustic lime to a moist 
atmosphere occasions slow hydration, accompanied by 
crumbling to a powder. Along with this change occurs 
an increase in volume of about one and three-quarters 
times that of the original lime. Such lime is air-slaked 
and is largely changed to the hydroxide Ca(OH) 2 . If this 
lime be exposed to water, it will further increase in vol- 
ume, but the paste resulting will be sharp and sandy in 
texture, and of much less value for mortar purposes than 
freshly slaked lime. In this case a portion of the CaO has 
no doubt combined with the C0 2 of the air, so that air- 
slaked lime is actually a mixture of lime hydrate and car- 
bonate. It is possible also to bring about the complete 
hydration of lime by steam at temperatures above boil- 
ing, without any change of volume or any sign of 
crumbling. 

Slaking may, therefore, be defined as the hydration of 
calcium oxide, quicklime, accompanied by an increase in 
temperature and volume. The increase in temperature is 
caused by the combination of the lime and water. It is 
an exothermic reaction, one in which heat is evolved. 
"Whether or not this heat becomes evident depends on 
the vigor and rapidity of the reaction. 

Slaking is commonly accomplished by the addition of 
sufficient water to cover the lime, and by further addi- 
tions as needed. It is desirable from the practical stand- 
point that the greatest possible increase in volume be se- 
cured in slaking. This is accomplished by careful con- 
trol of the amount of water throughout the process. The 
evolution of heat in such quantities as to generate steam 



within the mass is a necessity to the slaking process. 
At the same time, more water than simply that re- 
quired for hydration is essential. It is the expansion of 
the steam between the molecules of hydrating lime which 
forces them apart and caused the mass to crumble. As 
the particles are separated, the surrounding excess of 
water acts to remove them, as in the case if any fine sedi- 
ment, and as they float away in partial suspension, new 
surfaces of the lime are constantly exposed. A large 
excess of water prevents proper slaking by keeping the 
temperature so low that the necessary steam does not 
form. The mass then expands poorly, slakes slowly, and 
the product is lumpy. The lime is said to be ' drowned.' 

The result of too little water is a 'burnt' lime. In 
this case, the water forms a gelatinous film of hydroxide 
over the surface of the lumps which dries down enclosing 
caustic quicklime in the center, and so clogs the pores 
that further progress is much retarded or prevented. 
When too litle water is used, the action is apt also to be 
so violent in the case of 'fat' limes, that much or all 
of the moisture passes off as a vapor, because of the ex- 
cessive temperature developed. This frequently leaves 
the lime but partially hydrated, dry, and imperfectly 
slaked. 

Dolomitic limes slake more slowly and much cooler 
than do high calcium limes. The heat generated is 
due to the hydration of the calcium oxide, the magnesia 
remaining as the oxide during slaking. Although mag- 
nesium carbonate loses COo at a lower temperature in 
burning' than does the carbonate of lime, it hydrates only 
with difficulty and probably passes directly from oxide 
to carbonate in the hardening process. It is thus neces- 
sary to add the water required very gradually in slaking 
dolomitic limes in order to avoid 'drowning' and to se- 
cure the best results. 

The proper amount of water to use varies and can be 
ascertained for each individual lime only by actual trial. 
It is usually found more satisfactory to add the water in 
several different portions as slaking progresses, especially 
with the lean, slow slaking and dolomitic limes. In this 
way, by a little attention, the temperature of the slake can 
be controlled so that the best product is obtained from 



10 

the lime in use. 

The expansion of volume in slaking may be as high as 
three and one-half times with pure white limes. It is 
found to range from two and one-half to the figure 
named. Lean, so-called hydraulic limes, and dolomitic 
limes expand less. Increase in volume is ordinarily esti- 
mated by a comparison of the bulk of the dry quick-lime 
and of the paste after slaking. Careful experiments with 
samples of both high calcium and dolomitic limes made 
by the Ohio Geological Survey* show an increase in ap- 
parent volume for the white limes of from one hundred 
thirty-six per cent using twenty per cent less water than 
theoretically necessary for hydration, up to two hundred 
sixty-four per cent with forty per cent excess of water. 
With three hundred per cent excess, the increase was 
but forty-five per cent. The comparison was made be- 
tween the apparent volumes of the ground quick-lime 
and of the dry hydrate produced. Under the same con- 
ditions, a dolomitic lime gave one hundred ninety-three 
per cent expansion with a deficiency of twenty per cent 
of water, of two hundred ten per cent with the exact 
theoretical quantity of water, and of but about twenty 
per cent with an excess of water. The increase in volume 
is decidedly in favor of the white lime,' the smaller ex- 
pansion of the dolomitic lime being accounted for no 
doubt, by the fact that the magnesia takes up very little 
water in the slaking process. 

The actual increase is, as a matter of fact, more ap- 
parent than real. The calcium hydroxide produced from 
a weighed amount and accurately determined volume of 
calcium exide will occupy a space but thirty-five to forty 
per cent greater than the volume of the oxide. Few ex- 
periments have been made along this line and the above 
figures were obtained with a high grade white lime by the 
use of the Seger volumeter. 

If allowed to stand in the air lime deteriorates by the 
process of air-slaking already described. It also slowly 
absorbs carbon dioxide, which renders it of little value 
for mortar. After slaking, if the paste is not to be used 
at once, it should be ]3rotected from the atmosphere, since 
moist lime hydrate changes very readilv to the carbonate 



* S. V. Pe'ppel, Bulletin 4, Ohio Geol. Sur. (4th Series), p. 337. 



I 1 

by the absorption of CO*. Slaked lime is very commonly 
buried so as to be covered with several . inches of soil 
where it will keep for months without deterioration. 

Owing to the susceptibility to deterioration of the high 
calcium limes on the one hand, and the exceeding slow- 
ness with which dolomitic limes slake on the other, so 
called 'hydrated limes' are being put upon the mar- 
ket. The quick-lime is snbjected to a partial hydration 
or slaking at once after burning and before being sacked 
or barreled. The completeness of the hydration in the 
of live Ohio* products ranged from fifty-eight to 
ninety-four per cent, one hundred being taken as the 
best that is possible on a commercial scale. Specially 
designed and patented apparatus and processes are being 
employed in the hydration of limes, but it is believed 
that such special equipment is not necessary nor will the 
preparation of bydratecl limes, without doing so under 
a patent, make any person liable for infringement. At 
present but a single plant produces hydrated lime in 
Iowa. Others are contemplated in the near future. 

The desirable qualities of hydrated lime are (1) its 
convenience in use, for it is already pulverized and but 
little time is required to make a mortar by mixing the 
ingredients dry before adding the water;" (2) its lasting 
qualities, as it will keep much longer without detriment 
than the unslaked product. Magnesian limes are more 
commonly prepared in this way, and the saving of. time 
in their use is a very important commercial consideration. 
Hydrated magnesian lines are found by the Ohio Survey** 
to have specific gravities of 2.12 to 2.25. High calcium 
limes run about 2.45. A series of tests with an Iowa white 
lime gives specific gravities from 2.2 to 2.32 for the slaked 
lime, while the quick lime is 2.08. 

SETTING AXD HARDENING. 

In slaking, the lime takes water into chemical combina- 
tion, and becomes the gelatinous hydroxide. When this 
hydroxide is put in place as a mortar, it is said to set. 
This preliminary set is due to the loss of the water used 
in mixing which brings about a certain rigidity in the 

* S. V. Peppel. Bulletin 4. Ohio Geol. Sur., pp. 335-336. 
**S. V. Peppel. Ioc. cit. 



12 

same way so far as is known, that clay becomes hard on 
drying. Part of the moisture evaporates from exposed 
surfaces, but the larger proportion is in most instances 
absorbed by the porous brick or other masonry material 
with which it is used. The more rapid the set, that is, 
the more rapidly the mortar loses its water, the safer 
the construction, providing the proportions of sand and 
lime are such that shrinkage may be left out of account. 

A second process begins at once when the lime is ex- 
posed to the air. This is the absorption by chemical com- 
bination of carbon dioxide by which the lime returns to 
the carbonate condition, as it existed in the original lime- 
stone. The process is a slow one and may require years 
for completion, but this depends largely on the surface 
that is exposed and the thickness of the layer and por- 
osity of the mortar. A large number of chemical tests 
on small briquets having a minimum cross section of 
one square inch, made with mixtures of sand as high as 
6 to 1, and allowed to stand for a maximum period of 
one year, showed none in which carbonation was com- 
plete. This action is most rapid in the first few months 
until a crust of the carbonate forms on the exterior. The 
crust retards the process and at the same time protects 
the soluble hydrate within from being dissolved. The 
interior portions of large masses may therefore, never 
reach this final condition in hardening. 

Long contact of lime hydrate with finely divided silica 
is known to cause a reaction by which the silica com- 
bines with the lime forming a stable silicate of lime. The 
extent to which this reaction progresses depends on the 
physical and chemical qualities of the siliceous impurities 
in the lime or of the sand used with it. If these are very 
fine, chemical action is favored. Silicates, such as clay 
of feldspar, for example, are more susceptible to attack 
by the lime than is quartz sand. Hydraulic limes are apt 
therefore, other things being equal, to give a more dur- 
able final product than the purer limes. In the same way, 
muddy or clayey sand used with lime, although less de- 
sirable at the start, will likely contribute to the durability 
of the mixture in time because of the development of 
these stable compounds by the caustic action of the lime. 
In the case of silicates, it is probable that other elements. 



13 
especially alumina, also enter into combination. 

LIMB MORTAR. 

Sand. — Lime has a variety of nses in various industries 
but by far its most important application is and has been 
as a mortar in structural work, interior wall plastering, 
etc. For these purposes, slaked lime alone can not be 
used on account of the great shrinkage of the lime paste 
in setting and its lack of inherent strength when set. It 
is, at the same time economical to add some foreign ma- 
terial which is cheaper than the lime itself. The filling 
material commonly employed is sand. Most sands are 
composed largely of quartz grains, although fragments of 
feldspar and of many other minerals are often found in 
varying amounts with quartz. There is often also more 
or less of earthy or clayey matter in sands. 

In general, it may be said that the composition of the 
sand is not an important consideration. Any inert sub- 
stance which does not shrink nor deteriorate may be 
used. Ground limestone, for example, or the pulverized 
sand from any durable rock will serve the purpose equally 
well. 

The physical condition of the sand is, however, of 
considerable importance. The function of the lime is to 
serve as a binder to hold the particles of the aggregate 
together. If these particles are angular and rough, they 
afford good surfaces for the attachment of the lime. 
Sharp sand will therefore make a stronger mortar than 
one composed of rounded grains. Only sufficient lime is 
required to fill the voids and to form a thin film around 
each grain of the aggregate. The more nearly the voids 
are filled with the sand grains themselves, in other words, 
the smaller the percentage of pore space in the sand, the 
less the amount of lime needed. A sand composed of a 
properly proportioned range of sizes of grain will there- 
fore not only give the strongest product but will do so 
with the least amount of lime. Few sands as they occur 
naturally are composed of the proper range of sizes to 
give the smallest pore space. It is sometimes not difficult, 
and often may be a matter of economy, to correct a poorly 
proportioned sand by screening or by the addition of suit- 
ably graded materials. The voids in a sand are deter- 



mined readily with simple apparatus.* Separation into a 
series of sizes is quickly done by sieves of a number of 
different meslies. These two tests afford data as to how 
far a given sand departs from the ideal mixture of grains 
and indicate the size of grain and quantity to be added 
for correction. 

The sand grains should be practically in contact 
throughout the mass so that the lime paste forms merely 
a plastic film filling the interstices. Such a mortar when 
it has attained its final hardness may properly be re- 
garded as sandstone in which the cementing matter is 
lime carbonate. It differs from the natural stone only 
in its position and origin, being as strong, if properly 
made, and as durable as that quarried from natural 
ledges. 

White limes shrink much more in drying than do dolo- 
mitic limes. For this reason is it more highly important 
that the proper proporton of sand be used with the 
former. The binding or adhesive power of white limes 
is also less. This is evidenced in walls where the mor- 
tar separates readily from the brick and can itself often 
be crumbled in the fingers. Such defects are believed to 
be due more to poor mixing and wrong proportions of 
sand and lime than to any inherent quality of the lime 
itself. On the other hand, dolomitic limes possess great 
adhesive strength and not only form a denser mortar by 
binding the sand particles firmly together, but contrib- 
ute towards the stability of the wall by adhering to the 
brick or stone. 

TESTS OF LIME MORTARS. 

Although lime has been used as a mortar since very 
early times, and is of late being employed in various other 
ways in structural engineering work, few 'records of tests 
of those physical properties which make it of value are to 
be found. The purpose of the following series of tests is 
to investigate several of the physical properties of lime 
mortars, including the following points: (a) The influ- 
ence of slaking with increasing amounts of water; (b) the 
increase in strength with increased setting periods ; and, 

♦Standard Sand for Cement Work, M. J. Reinhart. Proc. 3d Ann. 
Convention Iowa Association Cement Users, Iowa Engineer Vol VII. 
No. 1, p. 34. 



15 

since in practice, limes are seldom used in the neat condi- 
tion; (c) the effect of varying proportions of sand on the 
strength of the mortar, and the rapidity of setting. There 
has also of late been considerable discussion as to the rela- 
tive merits of the white or high-calcium limes, and the 
brown or magnesian limes. 

To obtain definite data on these several points, the 
following plan was adopted in the beginning: Barrel 
samples of commercial limes were obtained from the prin- 
cipal producers in Iowa, and a few from bordering states. 
Samples of white lime were tested from Springfield, Mo., 
and Mason City, Iowa; of dolomitic lime from Viola, 
Iowa; Mason City, Iowa; Maquoketa, Iowa; and Eagle 
Point, Iowa. 

"While it was evident that the factors enumerated above 
were the important ones to be studied, with each lime it 
was necessary to carry on considerable preliminary ex- 
perimenting in order to be able to lay out an exact sys- 
tematic method of procedure. A provisional line of ex- 
periments was therefore initiated, using the white lime 
from Mason City. The quick-lime was slaked with per- 
centages of water ranging from the amount which wonld 
produce a dry powder as a minimum, to a maximum of 
300 per cent by weight. Slakings were then made with 
100, 150, 200, 250, and 300 per cent of water, calculated 
on the basis of dry quicklime as 100 per cent. From each 
slaking, series of briquettes were made with the follow- 
ing sand dilutions,* by weight: 

One part sand to 1 of lime, 1% of sand to 1 of lime, 
2 of sand to 1 of lime, and so on to 5 parts of sand to 1 of 
lime. Four sets of briquettes were made from each sand 
mixture to be broken at the end of four, eight, twelve and 
sixteen weeks respectively. Ten briquettes were used in 
each set from which to oDtain an average. 

Briefly then, from the lime paste obtained by slaking 
in each of six different percentages of water, briquette's 
were made with nine different dilutions of sand. Since 
four periods of set were to be allowed, with ten briquettes 
to be broken at the expiration of each period, a little 
arithmetical calculation will show that for each 

1, according to this plan, 21 GO briquettes would be 

standard river sand was used throughout the tests whose grains passed 
a twenty mes i 'linear) and remained in a thirty mesh - 



made. As the work progressed, it was soon discovered, 
however, that this general scheme required more or less 
modification according to the peculiarities of each par- 
ticular lime. 

HIGH CALCIUM WHITE LIMES. 
Lime from Mason City, Iowa. 

The limestone from which the Mason City lime is pro- 
duced comes from the Devonian beds, and has the follow- 
ing composition: 

Per cent 

Water 0.51 

Insoluble 0.63 

Alumina and iron oxide 0.71 

Lime (CaO) 54.59 

Carbon dioxide 42.89 

Magnesia (MgO) 0.47 

Carbon dioxide 0.5 2 



100.32 

Analysis of the commercial product: 

Quick-lime. After slaking. 

Insoluble 1.02 0.60 

Alumina and iron oxide 2.98 2.80 

Lime (CaO) 95.40 71.10 

Magnesia (MgO) 0.43 0.40 

Loss on ignition 0.00 25.60 



Totals 99.83 100.50 



A sufficient quantity of quick-lime was slaked at one 
time to make the full number (360) of briquettes as 
planned for each percentage of water. Precaution was 
taken in slaking to add the water in such quantities and 
to agitate the mass so as to facilitate the process and to 
obtain the greatest increase in volume with the amount 
of water employed. The lime paste was allowed to stand 
for twenty-four hours until all signs of heat had disap- 
peared and then put into air tight jars to be used as 
needed. All weights were calculated on a dry basis, the 
moisture being determined before each batch of both 
sand and lime was weighed out. In the ca^e of the 
higher percentages of water, it was necessary to drive off 
by careful heating, care being taken to keep the tempera- 
ture below boiling, some of the excess water, in order to 



17 

reduce the paste to a workable consistency. One man did 
the work, using his judgment to obtain as nearly as pos- 
sible the same consistency in every batch. Forty 
briquettes were made from each mixing. The briquettes 
remained in the molds until they could be safely removed, 
after which they were placed on edge on open shelves and 
allowed to harden for their respective periods. 

The tensile strength test was adopted as a means of ob- 
taining comparable results more because of its conven- 
ience and the uniform treatment to which each lime would 
be subjected, than as representing conditions which lime 
mortars would meet in actual use. As noted earlier, the 
principal function of a mortar is to serve as a matrix or 
adhesive to bind together particles of aggregates and sec- 
tions of masonry structure. Adhesion, therefore, and 
crushing strength tests would give more direct results. 
Such tests have not as yet been made. 

Eecords of tensile strength tests of lime mortars are to 
be found in the Report of the Secretary of War for 1896, 
Document No. 2, Volume II., part 5, on page 2839. These 
tests were made with paste slaked with three hundred 
per cent of water, ratios of sand from 3 :1 to 17.7 :1, and 
setting periods of twenty-eight and twenty-nine days and 
three months. Average strengths range in the short time 
tests from sixty-four pounds with a ratio of 8.8 :1 to 
twenty pounds per square inch with a sand lime ratio of 
17.7 :1 and, in the three months tests from seventy-one 
pounds with a ratio of 8.8:1 to thirty-six pounds with a 
ratio of 17.7:1. Tensile strength has also been investi- 
gated by the Ohio Geological Survey.* The following 
table, page 18, will indicate the results obtained. 

The period of set allowed in these tests is entirely too 
short for valuable results. But one briquette seems to 
have been made for each percentage of water. It is evi- 
dent that a much larger number should be used to obtain 
an average figure. 

A similar line of experiments made by Mr. George S. 

Mills, of Toledo, Ohio/!' affords results which bring out 
quite clearly the relative strength of the white and brown 



*S. V. Peppel, Bulletin 4, p. 337. 
tMunicipal Kiipineerinfr, Vol. 28, p. G. 



iS 



PHYSICAL TESTS OF OHIO LIMES. 



K1XD OF LIME 


Tensile strength of mortar after 

7 days. Mortar made by adding 

4 volumes of sand to I volume 

of quick-lime. 


REMARKS 


High calcium or 
white lime 


48.95 


Wa'er20% less than theory 
for complete hydration. 




70.6 


Theoretical amount of water 




50. 


!00 r r excess. Product, moist 
powder. 




42.36* 


*JBroke badly. Defective 
briquette. 100'/ excess. 
Heat applied in slaking. 




48.95 


200% excess, moist, lumpy 
mass. 




65.90* 


^Briquettes cracked beiore 

before going into machine. 

30O'r excess. Smooth 

stiff outtv. 


Dolomitic or 
brown lime 


24.48* 


*Bad briquette. 20 % less 
water than theory for 
complete hydration. 




72.2 


Theoretical amount of water 




58.* 


*Bad briquette. 20% excess 




81.90 


40% excess 




82.84 


Sticky, lumpy mass. 100% 
excess 




68.* 


*£ad briquette. Stiff putty. 
200% excess 



limes and the relation of strength to progress in setting 
and hardening of the mortar. The mortar was made with 
two parts sand to one of slaked lime by weight. The 
strength is expressed in pounds per square inch. From 
four to six breaking strengths were used for each time 







c a \ ex a 


^ C 1COLI 


1LO gXV CX. 


L XXX IXXC 




1 mo. 


2 mo. 


3 mo. 


4 mo. 


6 mo. 


1 Year 


Dolmite Lime 
High-calcium 
Lime 


30.7 


28.8 
36 . 6 


37.2 
39.2 


51. 


83. 
50.8 


92. S 
44.6 



The Mason City lime is a hot lime, which slakes vigor- 
ously and requires constant attention when water is 



19 

given to it. The quantity of water which would just 
leave the hydrate practically a dry white powder when it 
had cooled to the atmospheric temperature was found to 
he about 75 per cent of the weight of the dry hydrate. 

Table i below gives in detail the breaking strength of 
the briquettes made with the Mason City lime. A Fair- 
banks standard testing machine was used. 

From these figures, three sets of curves can be con- 
structed which will bring out in a graphic way the gen- 
eral trend of the results. One set, with sand-lime ratio 
and average tensile strengths as coordinates; a second set 
using the setting periods and tensile strength; and a 
third, based on the percentage of water used in slaking 
and the tensile strengths. 

Inspection of the table and of the accompanying curves, 
will show that, in general, the strength increases with in- 
crease of sand up to 2:1, 2.5:1, and possibly 3:1 in some 
cases and that beyond these ratios it decreases. Con- 
sidered with reference to the effect of different periods of 
set on the strength, little more is to be observed than an 
increase in all instances during the first two months. 
With the longer periods the change is not sufficiently 
pronounced to afford a characteristic curve. 

It is evident that the lengths of time allowed for the 
lime to set were too short for the maximum strength to 
be attained. This conclusion is supported by chemical 
determinations of the carbon dioxide absorbed which 
show that carbonation is in no instance even approaching 
completion at the expiration of sixteen weeks. Sufficient 
time should be allowed for the longest period for all the 
lime to return to the carbonate condition. Then the 
curves constructed according to the first two methods 
mentioned above would indicate clearly the progress of 
the gain in strength according to percentage of sand and 
setting period. 

Curve sheet No. 3 shows the relation between the per- 
centage of water used in slaking and the tensile strength 
of the briquettes. They are arranged in groups of four 
curves, each according to the whole-numbered sand-lime 
ratios. The general aspect of the five groups taken in 
conjunction with the tables, indicates a rapid rise in 
strength at one hundred to one hundred fifty per cent of 



20 



TABLE 1 



Slaked in 75% of Water 



£ 00 


~ 


Lbs. per sq, in. 


~ 


Lbs. per sq. in. 


- 


Lbs. per sq. in. 


°1 


50.5 


0J 


c 


£ 


■j. 3. 


D 


E 


E 


■y..z 


i> 


= 


= 


cu < 


C J 


be 


= 




C— ' 


tt 


z 


£ 


c — 


bl 


z 


z 


§c 


rt° 


^ 


"S 




~~ 2 


i^ 


/■ 


- 


~ — 




V! 


- 


K~ 


p^ 


> 


« 


._ 




> 


~ 


.— 


35 




T. 


._ 






< 


s 


§ 






^. 


S 




^ 


^ 


^ 


4 


1:1 


48.4 51.4 


38. 5 


1%:1 


45.7,50.5 39.5 


2:1 


54.5 64.4 


46.1 


8 




50.6 56.3 


47.5 




40.7,44.5 


35.0 




54.3 63.3 


48.0 


12 




56.160.4 


45.0 




47.1 oO.O 


44.3 




48.5 


52.5 


46.0 


16 




53.9 50.0 


42.0 




46.249.4 


40.8 




52.0 


55.9 


41.2 


4 


2%:1 


55.1 


60.4 


50.4 


3:1 


50.6 56.2 


41.9 


3%:1 


48.7 


55.0 


30.0 


8 




54.6 


58.6 


51.0 




52.6 58.4'44.5 




52.1 


56.0 


46.5 


12 




46.7 


48.5 


43.5 




48.151.0 45.9 




48.0 


54.3 


12.7 


16 




52.3 


56.9 


49.5 




43.4 48.6 33.6,' 
1 




32.9 


53.0 21.5 

j 


4 


4:1 


47.2 


51.4 


43.5 


4%:1 


43.7 53.0,35.0 


5:1 


43. v- 


58.4 38.0 


8 




17.8 


57.0 


37.0 




41.8 52.5,37.0 




45.9 


50.0 34.3 


12 




43.6 


49.5 


33.7 




42.6 46.6 38.4 




42.5 


51.4 28.6 


16 




41.5 


49.0 


28.8 




44.6 50.0 33.0 

| 1 




53.1 


•~>5.7 


50.0 


4 


5X:1 


37.1 


44.1 


28.8 


6:1 


36.0 39 6 34.6 










8 




37.8 


45.0 


32.6 




35.9 39.0 31.0 










12 




38.5 


44.1 


33.3 




33.139.4 29.8 










16 




38.6 


40.8 


34.9 




35.4 41.6 30.0 



















Slaked in 100% of Water 










4 


1:1 


47.3,56.2 


39.7 


l%:\ 


57.161.9 


53.01 


2:1 


55.9 73.6 45.4 


8 




56.464.8 


48.9 




60.5 68.7 


48.5 




72.3 94.7 


55.1 


12 




64.976.7 


52.5 




64.4J85.8 


45.4 




76.2 89.8 


54 1 


16 




62.973.3 


53.6 




73.2 91.6 


55.6 




67.9 83.6 


53.1 


4 


2X:1 


54.962.5 


43.8 


3:1 


49.9,65.6 


40.9 


3%:1 


51.0 61.3 


44.5 


8 




64.680.4 


53.5 




57.0,67.6 


51 .5 




54.0 62.8 


49.4 


12 




55.0,67.7 


41.0 




54.6 63.6 


45.0 




55.568.7 


50.0 


16 




57.6 


74.4 


36.7 




53.1 


58.1 


40.6 




56. S 65.7 


51.5 


4 


4:1 


52.8 


59.7 


41.2 


4X:1 


47.6 


55.4 


38.8 


5:1 


64.1 75.4 


52.5 


8 




53.8 


57.050.0 




49.6 


53.0 


44.5 




68.1 74.5 65.0 


12 




52.2 


58.745.4 




54.4 


58.0 


48.5 




63.7 69 3 57.0 


16 




49.6 


58.6 


43.0 




48.7 


52.0 


43.0 




65.8 72.5 59.0 


4 


5X:1 


56.4 


64.7 


.-,2.0 


6:1 


53.7 


59.2 


49.5 










8 




56.7 


62.0 51.5 




52.5 


54.5 


50.5 
49.0 










12 




60.4 


73.0,53.4 




54.7 


60.0 








16 




50.4 


59.441.0 




47.8 


55.0 31.3: 















Slak 


ed in 150 


% o\ 


Wa 


ter 








4 


1:1 


41.0 48.3,33.8 


1X:1 


47.1 


49.9 36.1, 


2:1 


45.0 53.2 38.0 


8 




40.9 48.9 37.0 




47.6 


64.6!36.1 




46.9 56.7 


40.4 


12 




45.8 55.3 34.0 




50.8 


59.8 


40.4 




52.168.3 


39.0 


16 




47.6 55.7 


39.2 




57.5 


74.5 


40.8 




62.081.6 


51.5 


4 


2%:1 


55.4 68.7 


38.8 


3:1 


60.7 


68.7 


45.7 


3%:1 


71.9 81.0 


61.8 


8 




59.8 78.1 


44.4 




54.0 


64.5 


47.5 




60.7,71.4 


41.4 


12 




56.6 76.3 


42.8 




63.7 


72.1 


51.0 




76.284.1 


69.7 


16 




55.4 79.9 


51.0 




77.3 


83.0 


66.3 




76.3J83.4 


64.3 


4 


4:1 


60.5 67.7 


53.5 


4%:1 


51.7 


59.4 


44.9 


5:1 


46.0.51.5 


40.4 


8 




63.9 74.5 


59.4 




58.9 


62.6 


53.1 




47.5 51.0 


45.0 


12 




69.9 76.8 60.6 




61.1 


64.3 


49.2 




49.6'48.2 


42.0 


16 




59.5 70.7 


49.5 1 




60.5 


68.4 


53.1 




60.2 75.5 


42.3 



(Continued next page) 



21 











Slaked in 200 


# of Water 










Sob 


T3 


Lbs. per sq. in. 




Lbs. per sq. in. 


T3 


Lbs. per sq. in. 


■jj 


S E 




6 


E 


3 c 




E 


E 


od c. 




F 


F 


Sg 


03.3 




3 




X.- 


<L> 


3 





x.t: 




■z 


•2 


<u £ 


o»J 


i£ 


F 


E 


oJ 


bo 


E 


E 


oJ 


fee 


F 


F 


.y = 


*2 o 




"S 




as 


2 

<u 


* 




1*2 




* 




K~ 


K 


> 


n 




04 


> 






« 


> 


rt 








< 


s 


£ 




<J 


& 


§ 




< 


§ 


S 


4 


1:1 


45.0 


60.6 


37.2 


IX: 1 


44.4 


58.3135.7 


2:1 


45.2 


54.6 


38.5 


8 




45.5 


62.8 


44.3 




51.0 


65.643.9 




57.3 


69.7 


45.9 


12 




45.2 


61.8 


42.6 




40.0 


57.134.7 




50.6 


61.2 


40.0 


16 




47.4 


53.1 


41.2 




48.5 


67.036.4 




53.4 


62.8 


46.5 


4 


2X:1 


41.7 


55.2 


33.4 


3:1 


46.9 


57.137.0 


3X=1 


46.2 


53.1 


38.0 


8 




51.2 


69.8 


38.8 




55.0 


72.4 43.9 




56.0 


67.0 


46.5 


12 




50.9 


61.8 


37.4 




49.6 


65.9:42.3 




55.2 


59.2 


52.0 


16 




60.6 


68.0 


53.1 




54.0 


58.248.4 




57.8 


60.8 


52.1 


4 


4:1 


40.6 


44.9 


38.0 


4%:1 


41.0 


44.138.6 


5:1 


43.8 


46.0 


39.8 


8 




+7.7 


57.3 


38.8 




53.2 


63.1:38.8 




46.3 


50.5 


42.6 


12 




52.9 


60.0 


47.5 




52.2 


57.4 45.5 




53.5 


59.6 


38.0 


16 




53.0 


57.0 


45.5 




54.9 


57.1 


53.01 




52.7 


54.5 


47.0 



Slaked in 250 % of Water 



12 
16 



12 
16 

4 

8 

12 



1:1 



2X:1 



4:1 



35.4137.6133.2 

43.2J49.0I36.0 
38.0 43.9 35.0 
40.0 45.2 36.0 



42.7 
50.] 
51.9 
58.9 

43.2 
43.4 



60.2 
63.9 

70.8 



38.8 
36.5 
40.4 
46.4 



64.0 35.0 
48.0J35.0 
53.0 56.6!49.0 



1X:1 



3:1 



4%:1 



138.9 
45.4 
41.2 
43.9 

52.6 

54.8 
56.8 
58.7 

47.5 

50.9 
54.5 



40.9 
53.2 
46.4 
50.0 

61.0 
63.6 
70.6 
69.0 

58.3 

58.0 
60.0 



33.0 
35.4 
36.8 
36.5 

42.9 
41.0 

45.2 
50.0 

37.4 
35.9 
45.5 



2:1 



5:1 



37.9 
48.6 
47.4 
51.8 

52.7 
48.5 
56.3 
58.0 

50.2 

56.6 
56.9 



41.0 33.0 
56.1.'44.1 
55.5|42.8 

58.942.0 

60.043.4 
55.140.4 
63.3|46.0 
62.0 57.0 

55.4 30.5 
62.2 42.4 
61.6 53.0 



Slaked in 300 # of Water 



4 


1:1 


38.1 


47.4 25.5 


1X:1 


35.6 


48.4 26.0 


2:1 


36.0 


48.4 


28.6 


8 




35.8 


54.2|27.3 




35.2 


53.6'28.8 




35.9 


43.9 


28.6 


12 




43.0 


58.328.2 




38.5 


54.627.8 




40.7 


53.5 


34.0 


16 




41.7 


57.826.6 




40.8 


51.034.3 




41.2 


52.1 


32.0 


4 


2%:1 


41.8 


50.0 35.3 


3:1 


40.0 


50.5 


32.6 


3X=1 


42.4 


50.0 


33.3 


8 




46.2 


51.040.8 




40.2 


53.0 


30.6 




52.1 


58.1 


45.2 


12 




51.1 


60.239.6 




46.1 


51.0 


36.0 




52.5 


55.0 


45.9 


16 




56.8 


63.8 50.0 




47.8 


54.0 


40.0 




46.7 


58.0 


35.0 


4 


4:1 


38.2 


46.5 


31.3 


+x--i 


39.7 


43.5 


22.8 


5:1 


40.7 


47.5 


35.0 


8 




39.2 


51.5 


31.9 




45.8 


00.0 


38.2 




48.3 


54.9 


42.7 


12 




37.6 


43.5 


28.8 




43.6 


48.5 


35.9 




46.4 


52.0 


43.0 


16 




43.0 


50.5 


40.0 




41.4 


49.0 


30.7 




46.1 


53.0 


30.0 


4 


5X=1 


37.8 


44.5 


34.0 


6:1 


41.7 


46.0 


36.6 










8 




46.7 


52.9 


38.6 




46.5 


51.3 


41.5 










12 




46.5 


52.4 


38.5 




47.7 


54.3 


43.1 










16 




46.5 


58.0 


43.2 




49.8 


55.0 


44.3 











22 




Percerttagi of sund" to Umt 




4-mo- curve 



5 Inked irt 
100 perc&ni wtttr 




*o> 



(.0 



40 



24 



Dots tndicotzta vrsc of f\mo cum . Oossts \t\6 i&att co ir$i of A-mti cmvi 




300 percent wr\\(t 



P.trcenfq^ oj sand fj lime. 

Sheet 1. White Lime from Mason City, Iowa. 



6-1 



23 










% i 

1 < 


s ^ 






V 

■I 
i I 




Slqkti lit 
/OOptrcenlwijUr 





3 + 

Pfrmri of st\ m months 



-Si 40 



Shkii in 
ZOOpituntwtfu 









5/qtad /it 
300ft,rua\wtikr 










. 





2 3 4- 

Per»oj/ of set in mont/is 






RqtlO 

Sgnd to lime 3 1 















4 ma 
2 mo 
/ms 



loo ZOO 30c 7S too zoo 300 7? 100 zoo 300 

Pereentfjgt 0f wjjttr used m slaking 



&o 



(6 





Mia 

5»nc/fj Iimt4' 


ft: 

I ma 


A 


^ 




Urna 
3 mo 
Ima 




Sqnd to Iimt4/- 


^ 


k 


^v 


7 


\ 


&= 


/ 


i mo 

Z "• 








■^ 


Ptf/O 

fW fa I<me5 / 




f 







V" 



75 too ZOO 300 75 /<n Zoo 300 7S too zoo 300 

ferctntq^t 0} wittr used in slqkmq 

Sheets 2 and 3. White Lime from Mason City, Iowa. 



24 

water, and as rapid a fall at two hundred which con- 
tinues through. the higher percentages. It is to be noted 
that one hundred per cent of water gives the highest 
strength with the 1 :1, 2 :1 and 5 :1 sand dilutions, while 
with the two middle members of the series, 3:1 and 4:1, 
the highest strength is reached with one hundred per 
cent. This may be but a coincidence, with results for 
only one lime at hand. The percentage theoretically 
necessary to hydrate the calcium oxide in the lime is but 
about thirty per cent of the weight of the dry quick-lime. 
The increase in strength with successively longer periods 
of time can also be traced from these curves. It will be 
further noted that the rapidity of increase is greater the 
higher the percentage of sand used. 

The experience gained and the results accruing from 
the foregoing tests of the Mason City white lime sug- 
gested certain changes in the general plan of the experi- 
ments. In all the tests whose results follow, the longest 
setting period is made one year, and sets of briquettes 
were broken at the end of three, six, nine and twelve 
months. The percentages of water used for slaking are 
the even hundreds up to three hundred per cent as a max- 
imum, with the exception of the white lime from Spring- 
field, Mo., in which case four hundred per cent of water 
was used, since it slaked to a dry powder with one hun- 
dred per cent. The lowest percentage is in all instances 
the largest possible amount that would leave the slaked 
product a dry powder. Only the whole-numbered sand- 
lime ratios are used in the later tests. 

WHITE LIME FROM SPRINGFIELD, MISSOURI. 

The limestone from which the Springfield lime is made 
has the following chemical analysis.* 

Per cent 

Lime Carbonate (CaCch) 99.46 

Iron Oxide (Fe20 3 ) 0.21 

Silica (SiO?) 0.33 



100.00 



*20th Annual Rep. U. S. Geological Survej-, Part VI (Continued) p. 415, 
also Bulletin 44, N. Y. State Museum, p. 924. 



23 

Analysis of the commercial product: 

Quick-lime. After slaking 

Insoluble 1.00 0.67 

Iron and Alumina (FesOa+ALOs) 1.80 1.11 

Lime (CaO) 94.70 73.20 

Magnesia (MgO) 0.40 0.43 

Loss by ignition 2.08 24.25 

Carbon Dioxide (COj) Trace 

99.98 99.76 

The Springfield lime is unusually pure and, as may be 
expected, slakes rapidly and with much heat. With two 
hundred per cent of water, it was fonud difficult to pre- 
vent the lime from 'burning.' Up to three hundred per 
cent of water, it was impossible to keep the paste thor- 
oughly mixed on account of the generation of steam and 
the violence of the slaking action. Three hundred fifty 
to four hundred per cent work best and give a uniform, 
well slaked product. 

It is unfortunate in any investigation if the person be- 
ginning the work can not carry it to completion. Even 
though the training of the experimenters be identical, 
personal equation always enters, and sometimes to a suf- 
ficient extent in small matters of manipulation, and in the 
exercise of judgment, to produce unexplainable irregu- 
larities in results. In the present experiments it was nec- 
essary to place the work in new hands at times during 
their progress. Lack of uniformity in the data which fol- 
low can in some instances be accounted for only by such 
changes, and yet it is not possible to assign absolutely to 
this cause variations that appear. Notwithstanding all 
minor deviations from the rule, however, there are re- 
vealed certain general truths that are brought out in the 
results given. 

In Table II are compiled the results of the tests of the 
Springfield lime and these are graphically shown in sheets 
4, 5 and 6 which follow . 

The curves on sheet 4 show that there is little change 
in strength after three months. In a few instances there 
is a slight gain, but in most cases the three, six and nine 
months figures run close, followed, as a rule, by a falling 
off at the end of twelve months. Inspection will show 
that this falling off is most pronounced with the high per 
centals of sand, 4:1, 5:1, 6:1, where the decrease has fre- 
quently hesiun at the end of three months. 

The diagrams according to percentage of water (Sheet 



26 



H 



w 


- 

CD 


H 


-u 


M 


C3 


— 1 

HH 


£ 


£ 


*R 




O 


o 


o 


% 


1— 1 




c 


z. 


.rt 


- 


CD 


w 


— ■ 


rti 


lx< 




o 


OJ 


z 




i— i 




pej 




- 




X 





CD "* CD 

O H X T^ 



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Sheet 4. White Lime from Springfield, Mo. 



28 



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Ptrctntiuji c/ vvqttr u5>tci in slqhincj. 

Sheet 5. White Lime from Springfield. Mo. 



2 9 



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lOCptrctnf wvoitr. 


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Rqiia 5and in limi* 

Shoe: C. White Lime from Springfield. Mo. 



3o 

5) are fairly uniform, all indicating a decrease in strength 
to two hundred or three hundred per cent followed by a 
rise with four hundred per cent of water. This final rise 
seems erratic, and its meaning is not at present under- 
stood. It will be noted that the greater ranges between 
highest and lowest tensile strengths are found where the 
lower sand-lime ratios were employed. 

Sheet 6 brings out clearly the decrease in strength with 
increase in the amount of sand. This is most prominent 
in the lower percentages of water where a 1:1 mixture 
is the strongest. With the two higher percentages, three 
hundred and four hundred, the average maximum 
strength is attained in the 3:1 and 4:1 mixtures. It is 
also conspicuous that the highest figures of all are 
reached with the lime when slaked with one hundred per 
cent of water which leaves it a dry powder. 

MAGNESIAN AND DOLOMITIC LIMES. 
Eagle Point, Iowa, Brown Lime. 

The limestone from which this lime is manufactured 
comes from the Galena beds of the Ordovician. Its an- 
alvsis is as follows: 



Insoluble S.6 5 

Iron and aluminum oxides (Fe^O: and ALOO 3.15 

Lime (CaO) 29.00 

Carbon dioxide (CO:) 22.60 

Magnesia (MgO) 17.12 

Carbon dioxide (CO.) 

TVater ■' 



99.46 



Analysis of the commercial product: 

Insoluble 2.01 

Iron and aluminum oxide? (FesOa and AlaOs) 6.60 

Lime (CaO) 58.19 

Magnesia (MgO) 33.48 

Loss on ignition Slight 

100.28 



The Eagle Point lime slakes sluggishly and gives a 
paste of brownish color. With all percentages of water 
employed there was little heating up and no steam was 



01 



generated. Slaking proceeded best with two hundred 
per cent of water and more rapidly than with lower per- 
centages. One hundred per cent gave a stiff piste, two 
hundred one of a readily and conveniently workable con- 
sistency, while the three hundred per cent paste was thin, 
and required the removal of the excess of water before 
use. 

Table III includes the results of the tests of this lime. 
On curve sheets 7, 8 and 9 are plotted the data of the 
table. 

The curves on sheet 7 again bring out the decrease in 
strength with age. It will be observed that the maximum 
strengths are attained at six and nine months, and that 
this almost universally falls off for the one year period. 
This falling off is most pronounced in general in the case- 
of the higher sand proportions. 

The influence of the amount of water used in slaking 
is shown on Sheet 8. It is impossible to make any gen- 
eralized statements from the diagrams. As a rule the 
highest strengths are found with the lower percentages 
of water. In the case of the 2:1, 5:1 and 6:1 sand-lime 
ratios, however, this is reversed and the three hundred 
per cent gives the highest figures. 

As with the white limes, the curves based on the sand- 
lime ratio are the most characteristic of the set. The 
lowest proportions of sand gave in all instances the high- 
est results. The decrease in strength with increasing 
sand is decided and rapid. The greatest range is seen to 
be with the lower percentages of water, the maximum 
tensile strength being shown by the 'powder' slaked, 
lime. 



32 



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176. 
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111.95 




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Ptrlori of 5ft in months 





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Period of st1 in months. 

Sheet 7. Dolomitic Lime from Eagle Point, Iowa. 



\d- 



34 



16 C 



t= I to 



-1+0 



5 i?o 



'5 60 
60 





Mil 

5o/idfplimf j:| 


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7J 100 200 3«o 75 100 2o0 "3*>o 7T ioq Zoo 3te 

krctrttqjji 8/ wqttr ustd in sinking 

Sheet 8. Dolomitic Lime from Eagle Point, Iowa. 






35 



'80 






T5 pint nl <*ottr 


cr 


t 










c 


\ 










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1 






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lOOptrcini wafir 












































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Into. 
3 mo. 
4mo, 
(2mo 



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5 '<© 

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c 


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4 / S;f 6:/ // 2:# 

flaf/o aand to \\mt> 







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300ptrc#nf water 












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9/T)ft 

IE/no 



Sheet 9. Dolomitic Lime from Eagle Point, Iowa. 



36 



MASON CITY, IOWA, BROWN LIME. 

The Mason City stone is Middle Devonian and belongs 
to the Cedar Valley stage. Its chemical analysis follows: 

Insoluble 1.34 

Iron and aluminum oxides (Fe-Oa and ALOs) 2.07 

Lime (CaO) 33.54 

Carbon dioxide (CO2) .26.35 

Magnesia (MgO) 16.99 

Carbon dioxide (CO2) 18.68 

Moisture 1.03 

100.00 
Analysis of the commercial product: 

Quick-lime. After slaking. 

Insoluble 2.32 0.80 

Iron and aluminum oxides (Fe 2 3 and AI2O3) 6.03 9.80 

Lime (CaO) 72.40 47.60 

Magnesia (MgO) 15.23 19.20 

Carbon dioxide (CO.) 0.10 3.50 

Loss on ignition 3.36 18.70 

Totals 99.44 99.60 

The Mason City lime slakes very slowly and consider- 
able care was necessary to secure a uniform product free 
from lumps. By a proper adjustment of the amount of 
water supplied as it is needed, and its distribution 
throughout the mass by stirring, a homogeneous paste is 
however readily obtained. 

In Table IV are arranged the data for this lime, which 
are also plotted on curve sheets 10, 11 and 12. 

The curves on Sheet 10 show for the Mason City lime 
the same tendencies as do the corresponding curves on 
preceding pages. The diminution in strength with the 
longest time period, while not universal, is so common as 
to be unmistakable. This is more pronounced in cases 
where the higher proportions of sand are used. 

Sheet 11 clearly shows the decrease in strength with 
increasing percentages of water. With few exceptions 
the maximum results come with the powder slaked lime 
from which the curves slope downward as the water per- 
centages increase. 

It will be noted also that the higher strengths corre- 
spond with the lower sand dilutions. With the powder 
slaked lime there is a decisive rise in all the curves at the 
2:1 ratio and this is less prominently the rule with the 
other curves on the sheet. The length of the setting pe- 



3; 



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CC 31 




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38 



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4-: J 



*f 12 3 6 <l I*. 

of set In months 

Sheet 10. Dolomitic Lime from Mason City, Iowa. 



6 

Ptnad 



39 



— 120 




£ 60 






















V 




\ 


5 


==: 






X 









6 mo 
?mo 



3ma. 



60 loe Zee joo 60 ioo 200 300 60 100 2.0© 300 



160 




Rqjtia 

Stni to I<nu4 : l 
























e 










"£,100 


^ 


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♦0 


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12 mo 





Rtfia 

5tnd \b limtS] 














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V 


y 


\ 


V 


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\ 









9 m n . 

fcma 

3 mo 
12 mo 





(Win 

5anJ 1ulimtfc:f 




















V 








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\ 




— =s 


- \ 


^ 



fro 'op 200 500 6« too 200 300 feo ioo 2oO JO 



fcmo 
3 mo 

'/ma 



(•trctntajt of *O.Ur 



kt-'d 



,lak( 



Sheet 11. Dolomitic Lime from Mason City, Iowa. 



40 










SI<LK£d HI 




















/* 


'% 












/ 


V\ 










frno 

37770 

12 me. 








V- 


















fc 

















/•V 27 3:/ 4- 

RuJie jftnd 1o lint 



180 

80 

140 
7\Q0 

-a 

£ 80 

in 

- *° 

•= +0 



mo 
mo 
mo- 



l\ 5\ 4-u S:\ 6> 

FU.T i o i«.nd to lime 







Slaked in 
200 jwr«nT niter. 


Imo. 
- iZrno. 

6 m«. 

3 mo. 






S\a.\ti n 
300ptrcfnfwal£r. 




















































V 




















>^ 


=d 


^s 






/ 








^V\ 





\. 


>5 


S 




' 
















X 


^ 









?-l 3t 41 

flat id sttfifl to iirtit 



2 me. 

Imo 



ftttTio sand folimt. 

Sheet 12. Dolomitic Lime from Mason City, Iowa. 



41 

riod appears to have no perceptible influence on this 
fact. 

MAQUOKETA WHITE LIME. 

A. A. Hurst & Co., Maquoketa, Iowa, Dolomitic Lime. 

EXCELSIOR WHITE LIME. 
O. W. Joiner & Son, Maquoketa, Iowa, Dolomitic Lime. 

The Maquoketa limes are produced from the Hopkinton 
beds of the Niagara stage. The composition of these 
strata is shown by the accompanying chemical analyses 
of samples from each of the companies: 



O. W. Joiner A. A. Hurst 

& Son & Co. 

Per cent. Per cent. 

Insoluble 0.51 0.58 

Iron and aluminum oxides (FejO.; and ALO.O 0.47 0.36 

Lime (CaO) 30.56 30.88 

Magnesia (MgO) 21.54 ■ 21.56 

Loss on ignition (CO: and water) 47.16 47.13 

Analysis of the unslaked commercial product (A. A. Hurst & Co.): 

Insoluble 0.63 

Iron and aluminum oxides (FecOs and Ah Oj) 2.10 

Lime (CaO) 60.60 

Magnesia (MgO) 35.70 

Loss on ignition 2.30 



The two samples of limestone analyzed come from the 
same horizon and compare very closely in composition. 
The treatment of the rock in the process of burning is 
exactly similar in both plants and the two limes are 
alike in appearance. Wood alone is used in the calcining 
process. 

The quick-limes slake slowly, as is characteristic of 
the dolomitic limes, and the heat crenerated is relatively 
small in amount. The Joiner lime required somewhat less 
water for the first slaking than the Hurst product and, 
in fact, less than any of the other limes tested. This 
quantity, as shown in the table, is fifty per cent of the 
weight of quick-lime used. 

The results of the tensile strength tests of the two 
Maquoketa limes are compiled in tables Nos. V and VI 
and are graphically represented by curve sheets 13, 14, 



42 



3* 

a 

^ LO 

t—l CD 

^ o 



CD 
<D 
E 

o 

T3 

c 

CO 


p 

< 


00 l- 

co l> cm co* 

CD CO I- CD 


OS LO CM CO 

d -t" -v ■*# 

CO 00 OS 00 


CO rH CD -h 
CONWH 

CO id Tt* CM 
t- t- CO l>- 


lO 

0) 

E 

o 

R 
CO 


P 

i 


-hh CM OS CO 

00 rH r-H 00 

NCtOio 


r" 
< 


111.6 
115.5 
119.4 
108.8 


98.61 
103.10 
109.71 

90.94 


CD 

E 
o 

T3 
P 

c3 
CO 


P 

i 

< 


^ CO OS 

rH LO -H CM* 

CO CO © OS 


115.7 
137.2 
120.6 
116. 


98.9 
108.92 
112.34 
105.4 


CO 
<D 

E 
J 
o 

T3 

C 

Rj 

CO 


R 
5: 


■hh CO CM 

co !>"• d co 

i- o o as 

i-H i-H 


1 

lo d cm hh 

i-H CO CO CM 


> 

< 


95.65 
117.33 
119.76 
108.56 


0} 

<D 

E 
"j 

o 

Xi 

a 

CO 


P 

03 

> 

< 


111.6 
103.9 
132.3 
141.6 


GO r-H LO 

d ^ -1- co 

rH r-< i— 1 i— 1 


121.82 
137.18 

158.72 
158.36 


CU 

E 

o 

•a 

o p 

mm 


p 

CTj 


85. 
100. 
139.3 
151. 


CO # <# 

CO •*? GO* CO 

co co as as 


109.68 
118.12 
169.61 
171.53 



Cu_ir! ~ P m 
H 2 





_ CO _ LO 

d >d oi lo 

lO lO lO Tfi 




# lo cd -r 
i- oi -^ hh* 

t- 00 I- CO 




61.4 
69.15 
60.3 
54.74 








CO CO CD 

CO CD O "* 

CO LO CD CO 




rH CD _ CO 
Tt" OS d t^ 
CD t— CD lO 




51.71 
64.1 
64. 
45.24 








id GO* CD lO 
CD t- GO CD 


CD 


95.1 

117.1 

99. 

84.1 


C 


83.59 
96.05 
91.4 

78.17 






o 

o 


> CD m CD 

GO* CO LO* CO* 

t^ CO CD lO 


no 

cu 

a 

X 


< as 

n d io co 
as o as as 


LO O t^ CM 

co" h ttjh d 

CO OS CO CO 








93.3 
100. 
102. 
101. 




CO _ CO 

lo d id ^ 

O CO CO CM 




99.5 
118.91 
118.1 
111.21 








91.8 
113.4 
114. 
120.1 




lO CD LO 

I>l HH t-I HH 

CM LO HH HH 


110.59 
130.7 
129.9 
132.09 


CO CD OS CM 





_ l- OS -H 

cm' cd co i> 

LO CD LO LO 




•r co* d d 

NCSON 




I- CD HH 

-* GO LO LO 

id go d id 

CO t- !>• CD 








as cm co 

lO -t N h' 
lONCOH 




HH CD OS 

00 d CO* CM* 
!>• GO t- GO 




CM 

as co cot- 
d id cm' i>* 

t- I> t— CO 








d cd t>* d 

CO I> CO LO 


rH 

CD 

+= 


85. 

98. 

100.9 

75.2 


c 


CO lO CO 
CO CO GO rH 

CM CO -t" CM 
t- CO GO CO 






o 
o 

Ol 




HN OS 

lo ^i* © co 

©OON 
i-H rH 


T3 
CD 

c3 


_ CD H CO 

oc -t" d d 

O CO CO o 
rH rH i— 1 rH 


C/J 


102.29 

119.84 

'13.65 

89.72 








84.1 
118.5 

88.6 
87.3 




CO CO LO 

id d cd d 

i— i lO CO CO 




97.02 
130.89 
113.08 
113.31 








00 

d t>" d cm 

t- t- OS CO 




CM 

id co* t^ d 

OS CO CM CM 




GO 
LO !>■ CO 

c6 d t> d 

CO O rH as 
rH rH 




CO CO OS CM 



as co t> lo 

Ol rH* |>.' 00 

LO t- LO HH 


lo cm t- as 

cd -t" i-h* d 

l- CO GO CD 


r-H t- as as 

CO CM H- to 

CO t^ OS CM* 

CO I- CD CO 




I- CM lO 

<6 r ^£ d ci 
co t» co -r 


78.4 
103.9 
101. 

71.3 


68.31 
86.61 
84.91 

60.89 




CM rH 

CO* LO CM* d 
t- GO t- hh 


. - ~. * ! 

GO* h-* CM* ^ 

co o as as 


CO CO O CO 
d — -' CO* !>■' 

go as co t- 




CO CM t- 

r-l GO -+' I>" 

as co as t- 


110. 
107.9 
115.4 
97.2 


98.42 
99.67 
89.98 
90.66 




. **. 

lO CO lO -t* 

oo o as co 


122.4 

136. 

130. 

111.8 


102.71 

115.49 

115.52 

92.91 




117.8 
111.7 
106.2 
118.1 


CO CM rH 

i>! go* co* t>l 

lO CD iO Tf 


134.33 

138.32 
131.82 
134.87 


co co as cm 



43 



3 c 

2 § 

— o 

— ,Q 
W A! 

O cc 



o 





E 

S 


Min . 

t s. 
lbs. 

per 

S(| > 
inch 


x re o t^ 

X 05 Cfi X 




S-JB»g| 


115.7 
1 25 . 

115.7 
118. 




> ■ ■ «3 tT u 
< _— ft«C 


98 :: , .> 

110.81 
102.47 
104.70 




l-5 

E 

c 


Min. 
t. s. 
lbs. 
per 
sq. 

111! Il 


85 . 
L08. 1 

90.7 
78.4 




M a x . 

t. s. 

lbs. 

per 
sq. 

inch 


180. 
1 12.9 

188.0 




£!!£*! 


104.7-1 

118.58 

118.20 




E 

CO 


Min. 
t. s. 
lbs. 
per 
sq. 
inch 


100. 

97. 
124.5 

96. 




Max. 

t. s. 
lbs. 
per 
sq, 

inch 


CO — iC- 

d co -# cc 

ei re — -t- 




Av. 

t. s. 
lbs. 
per 
sq. 
Inch 


05 X IC X 

NCO-*H 

ic ic" — ei 

O — re ei 








.. 
re 

o 

C 


Min. 
t. s. 
lbs. 
per 
sq, 
inch 


115. I 

102. 

110.8 

10S.9 




Max. 
(. s. 
lhs. 

per 
sq. 

inch 


188. 
141. 
189.2 
147.5 




Av. 

t. s. 
lbs. 
per 
sq. 

inch 


121.58 
125. 
189.2 
139.89 








ci 

<v 

G 

SO 


bim 


117.5 

178.2 
170. 1 
158. 




Max. 

t. s. 

lhs. 
per 
sq. 

inch 


157.7 
248.9 
21 1.8 

210. 




> an g a> a u 

< ■ — ~ B - 


118. ST 
218.52 
191.50 

1S2.9S 








E 
35 CO 


Min. 

t. s. 

lbs. 
per 
sq. 

inch 


70. 
100 
145.2 
121. 8 




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185. 
197. 
170.7 
180.0 




Av. 

t. s. 
lbs. 
per 
sq, 

inch 


112. (J 
110.05 
L59.38 
150.08 




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44 




IM 



= /60 






3-140 

5, 2fl 

5 /°° 

_^ 60 

o 

cr 

- 60 





SlQktd >n 

ZOO percent water. 








/ 


\ 




o 


>< 


% 


L 




\ 


^ 


~~— 








r 





Slaked in 








/ 








V 












^/ 




\ 


\ 






N 



2i 



4-1 



5.i 



Period of -scf in ^ months. 



/£. 





ilpkec 1 in 














/ 




V 




^? 


^ 


\ 


s^ 


^ 


\ 


^ 









/■■/ 






3 ^ °T /^ 3 & «=* I2L 

Period of *&T in months. 

Sheet 13. Dolomitic Lime, 0. W. Joiner & Son, Maquoketa, Iowa. 



45 



\to 


V 


AqhO 

Sond tclmt 1 1 




\ 






> 


\ 


J 




V 


f 


"in 






\ 


1 


l ~ bO 
AC 















lima 
3 mo 






Rqtio 

5on<) tolinu 3/ 







































Cma 
3'no 
<2ma 



SO /oo eco 3oc se loo zoo 300 30 /OO Zoo 300 

PLTCcnig^ °f wutir used in slihnq 






Rqfio 

Sqnd to lime 6 1 




















\ 






\ 


X- 


=■— ^ 









iUmo 



50 /oo 200 5oo so /oo zoo 300 so (oo Zoo 300 

Percentage i{ wntir used m shkinq 

Sheet 14. Dolomitic Lime, O. W. Joiner & Son, Maquoketa, Iowa. 



4 6 








5 1 q k t o in 












X 










\^5 
\ 












\ 




^ 














\\\ 











6010 



(80 1 

140 

-a 






5lqktd in 

£00 per ccn t Wfltfr 












/ 


\ 








7^ 










en 
c too 

•n 
80 








\V 






40 























g'l 3M 4:/ 5.1 6» 

Roho sunri to 







Slqkd in 

300 fir ctnl wqtcr 












V 










\ 


k 








\ 


^ 


^ 


i 


^>. 












\ 













hmt 



6m» 

3mo 

/2mo 



6» 



Sheet 151 Doloniitic time, 0. W. Joiner & Son, Maquoketa, Iowa. 




Period 0} 






Slaked in 
300ptrctntw«l£r 
































^ 











Of XT in 

Sheet 16. Dolomitic Lime, A. A. Hurst & Co., Maquoketa. Iowa 



6 

Period 






3 

months. 



<Z 



48 



iZO 



m 





A alio 

Si*! riL.tu l l 


/ 


k 






V 




7 


\ 


\ ' 























Rati* 

Sa«d tolim* 2t 










































9X)0 300 70 100 &AO 300 70 

P^rei/itajf oj ^vojtr usfd -in sinking 






Riha 

Sani ? 3 1imt4 1 












] 


A\ 




n^L- 


\%6ma 

I 



Raiio 

5a,nd 1« Iimt5 I 






Rat n 

Son i 'I'l'iftE i 












^h^NL 





60 

70 /CO £00 300 7C 100 £00 3©0 70 I0O 2C O 300 

Sheet ]?. Dwlomitic Lime, A. A. Hurst & Co., Maquoketa, Iowa. 



49 



200 






Por/dtr jkKt^ 
in 70ptrtu\l wa.hr- 






















a. 
= 140 












c 
21 uo 


















S ^ 


^ 


"— 




BO 













6 mo 

\l mp. 

3m» 







5laktd m 

I0O ptrctnl *oUr 


V 










s 


x 




























■ ' 

























<Z:I 31 +.1 




2S 3:1 4.1 J: 

Ratio so-nd to Jim*." 



l£mo 
6mo- 

5 mo. 



l 2 


1 


3S| 4 

sand fc li 


1 S 

mi 




b: 






SWvtd in 
3Q0 firctnlwaltr 











































. 














S , ~- 


tins 

IZltta. 

3 mo . 







t\ *l 4:1 3 

Ratio sand To iitnt." 



Sheet 18. Doloinitic Lime, A. A. Hurst & Co., Maquoketa, low 



50 

15, and 16, 17, 18 which follow. 

Joiner lime: Sheet 13 brings out very well the change 
in strength with increasing period of set. The powder 
slaked lime attains its maximum strength at nine months 
with the marked exception of the 1 :1 ratio in which case 
the curve continues upwards to the end of a year's time, 
and gives the highest figure of any mixture in the set. 
The other percentages of water give characteristic and 
fairly uniform curves, showing a maximum strength at 
six to nine months and a falling off on weakening after 
nine months' set. 

The curves on Sheet 14 are somewhat irregular but 
exhibit quite clearly the decrease in strength with in- 
crease of water for slaking. In general, the slope is down 
from the 'dry' slake through all higher percentages, 
although in a number of instances there is an unaccounted 
for rise from the minimum at one hundred or two hun- 
dred per cent. The position of the curve groups on the 
diagrams indicates the lowering strength with larger 
sand dilutions. 

Sheet 15 emphasizes the weakening effect of sand dilu- 
tions higher than 1:1 and 2:1 mixtures. In the majority 
of instances even proportions of sand and lime afford 
the greatest strength although a higher figure for 2:1 is 
not unusual. Higher ratios than these two, however, 
produce a marked falling off in tensile strength for all 
four time periods. 

Hurst lime : The curves of Sheet 16 run conspicuously 
uniform and show in general, the greatest strength at 
nine months. The usual lowering in strength at the end 
of twelve months is to be noted. As a rule this lime at- 
tained its maximum strength with one hundred per cent 
of water as shown on Sheet 17. The highest figures of 
the set are reached, however, by the powder slaked lime 
and a sand-lime ratio of 2 to 1. 

On Sheet 18 is brought out the relation between the 
strength and amount of sand used. With the powder 
slaked lime, 2:1 gives the highest results, while with 
the other percentages of water for slaking the trend 
of the curves is universally downward as the sand 
increases. 



5i 

"NEW PROCESS LIME." 
Viola Lime Works, Viola, Iowa. 

The Viola lime was manufactured from the Le Claire 
beds of the Niagara stage. The plant is now idle. The 
stone is highly magnesian and produces a lime of the 
following composition : 

Quick-lime. After slaking. 

Insoluble 1.20 1.00 

Iron and aluminum oxides (Fe^Os and Al-Os) 1.40 1.00 

Lime (CaO) •. 66.80 45.20 

Magnesia (MgO) 27.10 29.28 

Carbon dioxide (CO.-) 70 2.02 

Loss on ignition less CO.- 2.50 21.75 

99.70 100.25 

The commercial product takes water slowly and no 
slaking action becomes noticeable for some time. About 
five hours was required for complete slaking in sixty per 
cent of water, the mixture heating but slightly. With the 
higher percentages of water the time required is still 
greater and in all cases the slake is very cool. The lime 
does not melt to a paste as is usual, but remains in a more 
or less granular condition. The results of the tests of 
the Viola lime are tabulated in Table VII and plotted 
on curve sheets 19, 20 and 21. 

, A comparison of the data obtained in these tests with 
the results from the other limes of the whole series re- 
veals two notable departures. The breaking strengths 
are on an average higher, the maximum being nearly fifty 
per cent greater than the closest competitive value. They 
are remarkable also in that the strength almost without 
exception increases to the end of twelve months and this 
increase is most rapid, as shown by the sharpness of the 
curves on Sheet 19, when slaked with one hundred per 
cent water which gives the highest breaking strength of 
the set. The steepness of the curves between nine and 
twelve months is in many instances so marked as to ren- 
der of extreme interest the question, how long such in- 
crease would continue. A properly designed series of 
tests should be made along this line. 

Sheet 20 shows that the lime develops its greatest 



52 



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Sheet 19. Dolomitic Lime, Viola Lime Works, 
Viola, Iowa. 



54 






Ratio 
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Sheet 20. Dulomitic Lime, Viola Lime Works, Viola, Iowa 



55 



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to limi 



sheet 21. Dolomitie Lime, Viola Lime Works, Viola. Iowa. 



56 • 

strength when slaked in one hundred per cent of water, 
while on 21 is plainly shown the decrease in tensile 
strength following the addition of proportions of sand 
greater than one and two to one of lime. 

GENERAL CONCLUSIONS. 

While the foregoing series of tests are far from exhaus- 
tive and serve to open up and to suggest many questions 
that might be profitably investigated, the results obtained 
are, it is believed, sufficient to base upon them a few gen- 
eralizations. Some of the statements which follow are of 
facts that have long been regarded in practice but which 
have not before been proven by systematic experiment. 
The limes tested are types of high grade products and 
may be regarded as representative examples of pure 
white limes and of the magnesian or dolomitic class. The 
results therefore, are to be limited in their general appli- 
cation to these classes and are not to be construed as 
holding good for the impure or hydraulic limes. 

(a) The maximum strength reached within a year's 
time is attained at the end of a setting period of six to 
nine months duration. This is most pronounced where 
the higher percentages of sand are employed. The not- 
able exceptions to this rule are found with the lowest 
sand-lime ratios, the lower percentages of water used to 
slake and are most conspicuous in the strongly dolomitic 
limes. 

The cause for the diminution in strength after nine 
months is not known and results of chemical analyses to 
determine the amount of carbonation at the end of each 
of the four periods indicate that this process is in no 
instance complete at the end of a year's time. Carbon- 
ation has progressed to a minor extent only during the 
first six or even nine months. The change that occurs 
during the setting of the mortar is considered to be large- 
ly the crystallization of the lime hydrate. It is possible 
that such crystallization may produce a bond that is 
stronger than the carbonate. The process of carbonation 
displaces the combined water of the hydrate and may as 
a result actually weaken the cohesive strength of 
the mortar. If this be true, we would expect such loss 
in strength to continue till a minimum value is reached 



57 

which would either remain constant or, as the amount of 
carbonate becomes greater than that of hydrate and car- 
bonation approaches completion, increase again. It is 
within the range of probability that the ultimate final 
strength which might require years for attainment, would 
be greater than that reached in the first few months of 
setting. A set of long-time tests properly designed should 
yield valuable information along these lines. 

(b) In general, the greatest strength comes with the 
lower percentages of water used in slaking. Equal 
amounts by weight of water and of dry quick-lime give in 
the majority of cases, the highest results. Higher pro- 
portions are detrimental to tensile strength. This is more 
especially noticeable in the white limes. 

The generation of a considerable amount of heat, and 
consequently steam, seems essential in the slaking pro- 
cess, as explained earlier. Too little water leaves hydra- 
tion and therefore expansion in bulk, incomplete and the 
unslaked lime remaining receives its necessary moisture 
either slowly from the atmosphere or from the water 
used in mixing for use. The later slow hydration is not 
accompanied by the necessary rise in temperature or 
increase in volume. Too much water prevents the forma- 
tion of steam and maximum increase in bulk, and there- 
fore retards the slaking. A high excess may keep the 
temperature so low that combination between water and 
quick-lime may be evidenced by few if any signs of slak- 
ing whatever, for hours after immersion. It would be 
expected, therefore, that such a percentage of water as 
would produce the most vigorous slaking action and leave 
a satisfactorily moist paste would afford the best results 
when tested. This amount varies with different limes as 
noted in the consideration of each set of results. In every 
instance, however, the percentage giving the highest 
strength was that amount which gave the best slake and 
produced the most workable paste. 

(c) As a rule, the highest strength is given by the low- 
est proportions of sand, the curves being about equally 
divided between equal parts by weight of sand and dry 
quick-lime and two of sand to one of lime. 

Economy in the use of lime demands that as little as 
possible be used over that required to fill the voids and 



58 

to coat each grain of sand with a thin film. The sand 
particles should be in practical contact with each other 
throughout. The proportion of pore space in the stand- 
ard sand used in these tests is essentially forty per cent. 
(It will be recalled that this sand is a clean, rounded 
river sand and represents an average grade and quality 
such as is obtainable along the streams of Iowa.) The- 
oretically, therefore, a volume of slaked lime equal to 
forty per cent of the total space enclosed bv the sand is 
required to fill the open pores among the grains. If the 
lime could be confined to the pore spaces alone, still per- 
mitting the sand particles to touch at all possible points, 
such an amount of lime could be added without increasing 
the apparent volume of the sand, but this is not practi- 
cally possible. As noted on an earlier page (page 10), 
white lime hydrates range in specific gravity from 2.12 
to 2.32, and the magnesian averages 2.45. Assume an 
average for white limes of 2.22 and 2.65 for quartz sand. 
To be equal in volume to the voids in the sand there 
would be required in round numbers by weight thirty-six 
per cent of the dry lime hydrate. That is, with each sixty- 
four pounds of sand should be mixed thirty-six of slaked 
lime (estimated dry) to fill the space among the grains. 
There is required of the average dolomitic lime about 
thirty-nine in each hundred pounds of mixture to elimi- 
nate the voids. A liberal allowance would be forty per 
cent by weight in each case. 

The results of the tests show the highest strength with 
1 :1 or fifty per cent mixture. As lower ratios of lime and 
sand were not employed, it is impossible to do other than 
speculate on the possible results from such mixtures. It 
seems probable that mixtures as low in lime as theoret- 
ically required to fill the voids may show higher strengths 
than the lowest proportion used in the foregoing tests. 
This limit of the series could profitably be extended to 
include even the neat lime so as to make the results con- 
clusive. As the lime paste is ordinarily used in practice, 
it contains from fifty to sixty-five per cent of free mois- 
ture, the white limes carrying the larger amounts. In 
order to make calculations on the dry basis in mixing with 
sand, it is necessary to evaporate the water from- a small 
sample of the paste, weighing before and after to deter- 



59 

mine its percentage. Practically, also, sands as they 
come from the bank contain a considerable percentage of 
fine materia] which decreases the voids.* River sands 
range in the neighborhood of thirty-five per cent. The 
amount of voids can likewise be determined as directed 
in an earlier portion of this paper. 

(d) The white limes require more water to slake prop- 
erly, generate more heat in slaking, slake much more rap- 
idly and reduce to a more uniform paste than the mag- 
nesian limes. The dolomitic limes set and harden more 
slowly hut in many cases attain strengths so much greater 
than do the white limes as to he almost out of comparison. 
They will, therefore, stand greater dilutions of sand and 
still he sufficiently strong to meet the requirements of 
practical use. 



UBRARY OF CONGRESS 



I Ml I I 



029 942 424 8 



